libobjc/8562
(in libobjc:)
	* objc/hash.h (hash_string): Constify correctly.
	(compare_ptrs): Use direct compare.
	* objc/objc-list.h (list_nth): Rename index to indx to avoid shadow.
	* objc/sarray.h: Global rename index to indx to avoid shadow.

(in gcc/testsuite:)
	* objc.dg/headers.m: New test.

Co-Authored-By: Loren J. Rittle <ljrittle@acm.org>

From-SVN: r65461